Core for magnetic coils.



-L. ESPENSCHIED. 0on5 roa MAGNETIC cqlL; APPLICATION FILED SEPT H. 191

muted Jan. 1, 191a TM M m o m p A UNITED STATES PATENT ornron.

LLOYD ESPENSCHIED, OF HOLLIS, NEW YORK, ASSIGNOR TO AMEBIGAN TELEPHONEAND TELEGRAPH COMPANY, A CORPORATION OF YORK.

GORE FOR MAGNETIC COILS.

Specification of Letters Patent.

Application filed September 17, 1917. Serial No. 191,775.

To all whom it may concern:

Be it known that I, LLOYD EsPnNsoHmn, residing at Hollis, in the countyof Queens and State of New York, have invented certain Im rovements inCores for Magnetic Coils, 0 which the following is a specification.

My invention relates to improvements in the construction of magneticcoils, more par-' ticularly coils of the ring type used in telephonework as loading coils and the like. buch coils are usually constructedwith a core in the form of a magnetic ring made up of a bundle of wiresor laminations upon which the coil is wound. In order that the coil.shall be self restoring with respect to its impedance constants afterbeing subjected to the effect of magnetizing currents, the core is madediscontinuous by the provision of an air gap, whereby ademagnetizingaction occurs at the core pole faces of the air gap,tending to restore the core to normal conditions.

The provision of an air gap in the core results, however, in a decreaseof the permeability of the core as a whole, as well as an energy lossdue to stray magnetic fields at the air gap itself. It is the purpose ofthe present invention to overcome these defects, by increasing theefi'ective permeability of the air gap, without materially sacrificingthe beneficial stabilizing end efiects, (2'. 6. self demagnetizat1on) ofthe disconv tinuous core, at the same time decreasing the reluctance ofthe magnetic circuit as a whole. These'and other objects of theinvention may be attained by inserting inthe air gap of a ring core adisk of compressed iron dust, thus converting the air gap from a singleair gap to a serles of very minute and intermixed gaps. The core wouldbe then physically constituted of core sections composed of continuousiron interposed with short core sections composed of a composit materialwhich is non-continuous magnetically.

The invention may be more fully understood by reference to theaccompanying drawing, Figure 1 of which illustrates diagrammaticall theair gap core as usually constructed, ig. 2 illustrating the same asmodified in accordance with the present invention, and Fig. 3representing a modification of the structure of Fig. 2.

Referring to Fig. 1, the core is constructed in the form of two magneticsegments 1 and 2 of a ring, the segments being separated by non-magneticspaces 3 forming the so-called air gaps. Upon the segments 1 and 2 coils4 and 5 are wound, as

' shown, the two windings being thus inductively related. The segmentsmay, if deluctance of the core as a whole, by inserting in the air gaps,disks 6 of compressed iron dust, cons1st1ng of lron ground into veryfine particles, specially treated and insulated, and then molded intoshape under ity of very minute gaps separated by intermixed magneticmaterlal.

The same results may be attained by the modified construction shown inFig. 3, in which the core gaps are located within the coil windings,instead of between the windings as in Fig. 2. In this form the core isconstructed of segments 7 and 8 of compressed iron dust, the segmentsbeing separated by spacers 9 and 10 of magnetic material, and the coils4 and 5 being wound about the segments 7 and 8.

The introduction of the air gaps 3 into the iron magnetic circuit ofFig. 1 increases the reluctance of the magnetic circuit. As aresult, theinductance of the coil winding,

The air gap 1s thus for a given number of turns, is reduced below thevalue which would exist in the absence of the air gap. In the case ofcertain types of coils used in telephone circuits, it is desirable thatthe coil should be so designed that its impedance constants will returnclosely to the original values after saturation by service currents sothat no superposed magnetism will be retained. In other words the coilsshould be so designed as to have high grade residual stability.

The required degree of impedance stability can be most economicallyobtained by the use of discontinuous iron core circuits, the residualstability bein obtained by the demagnetizing action 0% the core polefaces at the air gaps. By using compressed iron dust or other finely ,7divided iron to bridge the air gaps as in Figs. 2 and 3, the relucofminute air gaps in the material has a self demagnetizing actionassociated with it. With reference to the terms air and air gaps ashereinbefore just used, it should be noted that the discontinuities inthe iron circuit are closed through insulating material,

which, however, is non-magnetic and has a permeability approximately thesame 'as air. The iron component of the gap spacer on the other hand,has a very much higher permeability than air, as a result of which thereluctance of the magnetic circuit as a whole is reduced and a greaterflux follows from a given excitation. Thus the mutual impedance betweenthe windings of a coil having the improved core structure can bemaintained at a higher value during the flow of service currents, thanif, as in the ordinary construction of air'gap coils, a material havinga permeability of unity should-be used as a gap spacer.

While the invention has been illustrated and described as embodied incertain specific forms, it is apparent that many and widely diversifiedstructures may be used for attaining the desired ends without depart ngfrom the spirit of the invention, and it w1ll therefore be understoodthat all such structures as fall within the scope of the appended claimsare to be considered as wlthin the purview of the invention.

What is claimed is: v

1. A magnetic coil having a core the magnetic circuit of which isdiscontinuous, and p means for bridging the discontinuities of Saidcircuit consisting of partlcles of magnetic material separated bynon-magnetic spaces. 1

2. A magnetic coil having'a core the magnetic circuit of which isdiscontinuous, and means for bridging the discont nuitles of saidcircuit consisting of magnetic elements separated by non-magneticspaces.

3. A magnetic COll comprlsmg a core provided with a gap, and means forbridging said gap consisting of magnetic particles separated bynon-magnetic spaces.

4." A magnetic COll comprising a-core provided with a gap, and a fillerfor the gap, said filler consisting of finely divided iron, insulated,and compacted under very high pressure.

5. A magnetic 0011 having a core of magnetic material, a gap in saidcore to render said core self demagnetizing so that the impedanceconstants of the coil will readily return to their normal value afterthe coil has been subjected to the effect of magnetizing current, andmeans to reduce the reluctance of the air gap without materiallyreducing the self-demagnetizing eflect of the core, comprising particlesof magnetic material arranged in said gap, said particles beingseparated by non-magnetic spaces.

6. A magnetic coilhaving a ring core, said core being formed ofsections, certain of said sections being of magnetic material, and otherof said sections being composed of magnetic particles separated bynon-magnetic spaces.

7. A .magnetic coil having a ring core, said core being formed ofsegments of magnetic material, the ends of the segments being separatedby gaps, and filler members for said gaps consisting of particles ofmagnetic material separated by non-magnetic spaces.

8. A magnetic coil having a core of magnetic material, an air gap insaid core to render said core self I demagnetizing so that the impedanceconstants of, the coil will readily return to their normal value afterthe coil has been subjected to the effect of magnetizing current, andmeans to reduce the reluctance of the gap Without materially reducingthe self demagnetizing effect of the core.

9. A magnetic coil having a core, said core consisting in part ofcontinuous magnetic material, and in part of discontinuous magneticmaterial comprising magnetic elements.

separated by non-magnetic spaces.

10. A loading coil having a core provided with a gap, and means to fillthe gap comrising minute particles of magnetic material separated bynon-magnetic spaces.

11. A loading coil having a core of magnetic material, a gap in saidcore to render said core self demagnetizing so that the impedanceconstants of the coil will readily return to their normal value afterthe coil hasbeen' subjected to the effect of magnetizing current, andmeans comprising finely divided magnetic material separated bynonmagnetic spaces to reduce the reluctance of the gap withoutmaterially reducing the self demagnetizing effect of the core.

In testimony whereof, I have signed my name to this specification in thepresence of two subscribing witnesses, this tenth day of September,1917.

LLOYD ESPENSCHIED. Witnesses:

R. S. SURLIFFE, ALFRED KAUFMANN.

